1. Field of the Invention
The present invention relates to a duplex type coating apparatus which is capable of simultaneously applying a coating liquid to opposite sides of a web such as an elongated fabric, a plastic film and a metal sheet.
2. Description of Related Art
One known duplex type coating apparatus is a twin-blade type coating apparatus.
The twin-blade type coating apparatus includes a pair of dies arranged at opposite sides of the path of travel of a web, and a pair of blades disposed above the pair of dies. A coating liquid is applied from the pair of dies to opposite sides of the web while the web is being moved up along a vertical path. Thereafter, the blades scrape excess coating liquid so as to maintain the thickness of a coating constant (U.S. Pat. No. 4,231,318).
However, a disadvantage with this arrangement is that the thickness of the coating is subject to change when lateral displacement of the web occurs.
To this end, there has been proposed another duplex type coating apparatus.
Specifically, a coating liquid is fed from a pair of dies under the same pressure while a web is being moved center of the pair of dies. If the web is displaced either to the right or left, then the die is moved so as to change the pressure of the coating liquid to provide a constant coating thickness (JP-A-03072976).
To provide a constant thickness, the duplex type coating apparatus requires movement of one of the dies. The adjustment of thickness in this way is, however, difficult.
Accordingly, the present invention provides a duplex type coating apparatus which readily ensures constant thickness of a coating on opposite sides of the web.
Recently, a portable cellular telephone or portable informative terminals have come into increasing use. To this end, a spiral electrode type lithium battery is fabricated on a mass production basis. When the litium battery is manufactured on a large-scale, a slurry composite material (coating liquid) mainly consisting of an electrode activating substance is coated on a hoop member (web) mode of a bandlike copper or aluminum foil. In that case, it is necessary to form coated and uncoated areas of predetermined lenghts, respectively, in an alternative fashion and it is also necessary to apply coatings at the same position on both opposing surfaces of the web. Moreover, the coated and uncoated areas must be formed at the same position on the opposite sides of the web.
These two conventional duplex type coating apparatus are able to continuously apply a coating liquid to the web, but unable to alternately provide coated and uncoated areas on the web.
Accordingly, the present invention further provides a duplex type coating apparatus which can provide a coating on opposite sides of the web and allows for intermittent coating.